This invention relates to speed reducers, in particularly those with very low ratio and unique transmission which is able to transmit higher torque levels than prior art transmissions. Moreover, this invention extends to a combined transmission system that transmits an oscillating input into a single direction output.
Transmissions are utilized to transmit rotation for a variety of purposes. The term "transmission" as utilized in this application, does not specifically refer to a vehicle transmission, although it would extend to such transmissions. Rather, this invention extends to any system wherein a source of movement is transmitted through a driving member to move a driven member.
Worm/worm gear transmissions, in particular, speed reducers, are well known in the mechanical power transmission field. The gear is driven by the rotation of the worm with which it meshes. The rotational speeds of the associated shaft of the gear are a function of the number of teeth on the gear and the number of threads on the worm. The worm may be single or multiple threaded. The prior art worm/worm gear transmission had 12 or more teeth. Even American National Standard "Design of Industrial Double-Enveloping Wormgears" (ANSI/AGMA -6030-C87) recommend 24 as minimum number of gear teeth. Furthermore, enveloping angle of any well known worm is not more than 30.degree..
The prior art transmissions have not successfully transmitted high torque levels. One common type of transmission is a one-way clutch. In these known systems (U.S. Pat. No. 5,333,517 by Rodney Bryson, Aug. 2, 1994) rollers, or other drive members are engaged within notches or openings in a driven member. The rollers engage and move the driven member when rotation is transmitted in the first direction, but will slip when rotation is transmitted in the second direction. This invention has ratio of 5 between worm and worm gear, but the number of threads on the worm is more than one, and this worm does not have self-lock feature. These types of clutches have enjoyed wide usage, but have been unable to transmit high torque loads. One proposal suggests using a pair of such clutches with an oscillating input to perform as a part of a vehicle transmission. Due to the low torque load, this system would be impractical. Main disadvantage of these types of clutches are discrete character of changing of contact. It leads to mechanical shocks during every new contact between driving and driven elements. Drive system for providing speed in a single rotational direction from a reversible input also well known (U.S. Pat. No. 5,333,517 by Rodney Bryson, Aug. 2, 1994). But this system has a gear train with some backlashes and it is not able to provide a small amplitude of vibration. Besides input and output shafts are perpendicular to each other, and therefore this drive system can not be used in many applications.
In one system disclosed in Soviet inventor certificate number 1,495,110, 1989, granted to the inventor of this invention, a self-locking transmission is utilized to transmit rotation. In the disclosed system, a worm and worm gear combination are utilized to transmit rotation. The rotation is transmitted utilizing the engaged teeth and thread of the gears such that there is no relative movement between the two gear members during this rotation. With such a system, many valuable benefits result. In particular, one is able to accurately and efficiently transmit rotation through the self-locking transmission. Main advantage of these types of clutches is continues contact between driving and driven elements.
In addition, the standard power supply utilized with such systems has difficulty allowing any of the structure to make a free turn of 360 degrees. Instead, electrical supply lines have typically limited the operative members to a restricted range of rotation. This is, of course, undesirable.
The term "self-locking" as it is utilized in this application to describe the inventive worm and worm gear combination, means that the teeth of the worm gear when in contact with the thread of the worm, are capable of rotating the worm about the axis of the worm gear. The teeth do not slip on the thread causing the thread to rotate about its own axis. By carefully selecting the material of the respective teeth and threads, and the respective angles, a worker of ordinary skill in the art would be able to achieve this goal.
However, there are some deficiencies in the system disclosed in the prior inventor's certificate. This invention and the related co-pending application of the same inventor, Ser. No. 08/353,797, and PCT International Application No. PCT/US95/15938, disclose improvements to the prior art system, and PCT International Application No. PCT/US96/02918.